单选题During working of an air compressor, （） should be drained.A inter coolerB cylinderC outlet pipeD inlet pipe

正确答案：Purifier :the different gravity of two types of liquids: water and oil .the centrifugal force of the water move towards the outside of the disc while the oil ,which is smaller in gravity shall move toward the center of the disc .this makes the seperation of the two liquids . Oil water separator : (1) pump bilge water into first chamber :polymerization of the oil on the gathering plates ,(2) and then through a fine filter (15ppm) separation of water and oil ,(3)discharge of the water overboard via 15ppm monitor and the oil into oil sludge tank .Air compressor :take into the air from the outside atmosphere and compress it with the up going piston .then ,cool the compressed air .then compress the air once again until it reaches the stated pressure (depending on the air bottle allowed pressure ) For the maintenance of the air compressor ,fistly ,must check to make sure that the suction valve and outlet valve to be sealed ;then make periodical lifting of the piston to make the pistons are in good condition .must check the crankcance lube oil everyday .

正确答案：The unloader on air compressor is used to reduce the high starting torqueduring starting and also provide a means of draining out the accumulating oil water .